> How is forcing the guy to sign away his voting rights while he was in the hospital legal?

Well, the concern from the standpoint of the other parties would that he would die, and his voting rights pass on to someone completely non-technical and/or non-entrepreneurial. I can see that it makes perfect sense to protect themselves against that eventuality.

Maybe it'd be better to have terms to convert to non-voting shares at death or permanent incapacity, with voting rights to be exercised in proportion to the other votes cast during temporary incapacity. But that could definitely get hairy too.

Being in a hospital isn't duress. Threatening to put someone in the hospital is duress. He might have had a lack of capacity argument, that is he was so out of his mind that he was unable to sign a contract, but I am not sure if that applies either.